Fluid drilling heads are utilised in a number of different borehole drilling applications and typically use a rotating head with a number of nozzles from which issue high pressure jets directed to break and erode the rock face in advance of the drill head. Fluid drilling heads of this type are described in international patent application PCT/AU96/00783.
One difficulty with fluid drilling heads of this type is controlling the direction of the head. In most applications it is highly desirable to achieve directional accuracy in the formation of a bore hole particularly in situations such as the draining of methane gas from coal seams preparatory to mining. In such situations, it is critical to achieve an even pattern of drainage bores, and to ensure that the bores are accurately placed to pass through proposed roadway locations in the mining operation.
In the past it has been difficult to accurately control or steer a fluid drilling head of this type which is fed via a flexible hose, typically either from a surface drilled location via a tight radius drilling configuration, or from an underground location for cross-panel, mine development, and exploration drilling.